Blind rivet with internal mandrel supporting element



Sept. 25, 1962 E. J. BURRELL 3,05 I

BLIND RIVET WITH INTERNAL'MANDREL. SUPPORTING ELEMENT 5 Sm les-Sheet -1M 24, l 58 Filed arch 9 2 5 1 I Sept, 25, 1962 'E. J. BURRELL BLINDRIVET WITH INTERNAL MANDREL SUPPORTING ELEMENT Filed March 24, 1958 5QSheets-Sheet 2 Sept. 25, 1962 E. J. BURRELL BLIND RIVET WITH INTERNALMANDREL SUPPORTING ELEMENT Filed March 24, 1958 5 Sheets-Sheet 3 BLINDRIVET WITH INTERNAL MANDREL SUPPORTING ELEMENT Filed March 24, 1958-Sept; 25, 1962 E. J. BURRELL 5 Sheets-Sheet 4 P 1962 E. J. BURRELL BLINDRIVET WITH INTERNAL MANDREL SUPPORTING ELEMENT Filed March 24, 1958 5Sheets-Sheet 5 United States Patent 3,055,255 BLIND ET WITH INTERNALMANDREL SUFPURTENG ELEMENT Edward James Burr-ell, Woodiey, England,assignor to Avdel Limited, a British joint-stock company Filed Mar. 24,1958, Ser. No. 723,497 Ciaims priority, application Great Britain Mar.25, 1957 7 Claims. (Cl. 85-40) This invention relates to blind rivetingin which tubular rivets are expanded or clinched into position in thework pieces to be riveted by pulling a mandrel therethrough, especiallyto blind riveting by means of a mandrel that is itself non-deformed inthe clinching or expanding operation, as is essential in blind rivetingby means of a magazine type gun in which the stem of a non-deformablemandrel carries a supply of tubular rivets threaded thereover.

The present invention has for an object to provide improved rivetingwith a tubular rivet and mandrel both so shaped as to ensure effectiveclinching of sheets.

In accordance with the invention, a high clench headed tubular rivetwhich may be upset with a broaching mandrel has a shank formed with arelatively strong zone at or near its tail and with a relatively weakzone intermediate its head and the strong zone.

Preferably the strong ZOne is constituted as an external flange orthickened wall at or near the tail of the rivet. The weak zone may beformed by making the wall of the rivet bulbous, or slotting it orthinning it.

In accordance with another feature of the invention, the headed tubularrivet may be formed with an internal conical lead-in to the weak zone.

According to another aspect of the invention, a high clench headedtubular rivet which may be upset with a broaching mandrel has a shankwhich is formed with a reinforcing flange at or near its tail end andalso, at least at that part thereof which when the rivet is firstinserted in the registering apertures formed in two or more members tobe riveted together lies between said reinforcing flange and themembers, with a relatively weak zone which is capable of expansion underlongitudinal pressure from the mandrel less than that required to expandthe reinforcing flange.

The formation of the shank so as to be capable of such expansion may beeffected in various ways; for example, the rivet may have a parallelbore and be longitudinally weakened by slitting or otherwise at at leasttwo places spaced from one another around its circumference, or it maybe formed with a waist, the wall thickness of which is preferably lessthan that of the remainder of the shank.

The rivet may be used with a mandrel the stem of which is a friction fitwithin the rivet.

In addition, the dimensions of the rivet and the mandrel used therewithare preferably such that in finally passing through the shank the latteras well as the reinforcing flange at its end is expanded thereby.

In accordance with a still further feature of the invention, the head ofthe mandrel where it joins the stem is of substantially hemisphericalshape rather than conical to assist in the expansion of the shank andtight clenching before the reinforcing flange is expanded.

Alternatively, the head of the mandrel where it joins the stem may beconical but of greater included angle than is appropriate for rivetswithout a reinforcing flange as set forth above, the included anglebeing dependent upon the axial thickness of the flange, said thicknessbeing reduced as said angle is increased.

Five constructions of the invention will now be described by way ofexample with reference to the accompanying drawings in which:

FIGURE 1 is a view in sectional elevation of one emice bodiment of arivet in accordance with the invention.

FIGURE 2 is a view in elevation of a mandrel employed with the rivet inaccordance with the invention.

FIGURE 3 is a view in elevation of the rivet threaded on the mandrel andinserted into registering holes in the work to be riveted.

FIGURE 4 is a view in elevation of the rivet mandrel assembly showinginitial expansion of the rivet.

FIGURE 5 is a view in elevation of the upset rivet and of the mandrelpulled therethrough.

FIGURE 6 is a view in sectional elevation of a rivet constructed inaccordance with another embodiment of the invention.

FIGURE 7 is a view in sectional elevation showing the rivet asillustrated in FIGURE 6 threaded over the mandrel and inserted inapertured holes in the work to be riveted.

FIGURE 8 is a similar View to that of FIGURE 7 illustrating the initialexpansion of the rivet after the initial pull on the mandrel.

FIGURE 9 is a view of the upset rivet and of the mandrel pulledtherethrough.

FIGURE 10 is a plan view of FIGURE 9.

FIGURE 11 is a view partly in section of another embodirnent of theinvention.

FIGURES 12 to 16 show progressive stages of rivet breaching employingthe rivet and mandrel as illustrated in FIGURE 11.

FEGURES 17 and 18 are views in elevation of another embodiment of therivet.

FIGURE 19 is a view similar to that of FIGURE '17 except that a splitring is inserted in the rivet head counterbore.

FIGURE 20 is a cross-sectional plan view on the line X-X of FIGURE 19.

FIGURE 21 is a sectional view of a modified form of the invention.

Referring to FIGURES l5 of the drawings, a parallel bore rivet l isformed with a head 2 at one end of its elongated shank 3 and with areinforcing flange 4 at its other end. P our circumferentially spacedaxial incisions 5 formed in the shank 3 are of such length and solocated lengthwise thereof that when the rivet 1 is placed in the hole 6in the sheets 7 and 8 to be riveted, said incisions 5' extend for ashort distance into said hole 6. These incisions 5 adapt the portion ofthe shank 3 protruding from the remote side of the sheet 8 to expandduring the broaching operation as will be later explained. The rivet 1is threaded tail first over a mandrel 9 having a stem 16 the diameter ofwhich is only slightly smaller than that of the internal bore of therivet 1 so that the rivet 1 is a close sliding fit on the stem 10 of themandrel 9. Where it joins the stem 10 the head 11 of the mandrel 9 is ofsemicircular longitudinal cross-section or has a semi-spherical outlineas indicated at 12. It will be observed that the diameter of the flange4 of the rivet 1 is slightly smaller that that of the registering holes6 in sheets 7 and 8 to be riveted so as to provide sufficient clearancefor the mandrel 9 and the tail end 4 of the rivet 1 to pass through theholes 6. The free end of the mandrel stem 10 is inserted in a knownriveting gun or appliance, the head 2 of the rivet 1 bearing against thefront jaws (not shown) of the gun which act as an anvil against whichthe rivet head 2 bears during breaching as the rivet 1 is expanded.

In use the rivet 1 threaded over its mandrel 9 is inserted in aperturedholes 6 in sheets 7 and 8 (FIG. 3), the initial pull on the mandrel 9during breaching causes the rivet shank 3 to expand around the areawhere the shank 3 is weakened by the incisions 5. Actually the portionof the shank 3 expands into a lantern shape as can be seen from FIGURE4. Upon completion of this expansion the mandrel 9 continues to pull theflange 4 of the rivet 1 into abutment with the sheet 8. After this hastaken place the mandrel 9 continues to pull the sheets 7 and 8 together.When the sheets are tightly clamped the increased force on the mandrel 9now expands the reinforcing flange 4 and clears the head 11 of themandrel 9 through the rivet bore and so expands the rivet shank materialthus radially filling the holes 6 in the sheets 7 and 8, and at the sametime further longitudinally constricts the rivet shank 3. This resultsin additional clench of the sheets 7 and S. It should be emphasized thatthe bore of the rivet 1 should be a close sliding fit on the stem 18 ofthe mandrel 9 otherwise the expansion of the rivet shank 3 would not beuniform and not in axial alignment. The mandrel 9 for placing the rivet1 has a specially designed head 11 which is substantially sphericallyshaped at its junction with the stem 1t so as to give maximum endloading. It will be understood that this rivet method employs a mandrelwith a thicker stem than is usually employed in magazine type rivetingguns thereby lessening the chances of mandrel breakage and at the sametime permitting a greater degree of clench.

In the modification of the invention as illustrated in FIGURES 6 to theshank 3 of the rivet 1 is formed with a bulge 13 in that part of theshank which is adapted to form the tail. This bulge 13 is formed byexpanding a portion of the shank of an initially parallel bore rivet,for example by hydraulic means, until the bulge 13 reaches an externaldiameter such as just to pass through the holes 6 in the sheets 7 and 8to be riveted. For example, for riveting holes of A" diameter theexternal diameter of the bulge 13 would be approximately .248. Theformation of the bulge 13 causes a reduction of the wall thickness ofthe shank '3 at the locality where the bulge 13 is formed so that thisarea when subjected to longitudinal pressure becomes easily expansible.As can be seen from FIGURE 7 the bulge 13 extends from approximately theremote side of the farmost sheet 8 to be riveted in the direction of thereinforcing flange 4 of the rivet 1 and becomes more pronounced midwaybetween the farmost sheet surface and the reinforcing flange 4 leaving anon-deformed portion 13a of the shank between the flange 4 and the bulge13. The initial pull on the mandrel 9 causes the bulge 1-3 to spreadoutwardly; at this time the bulge 13 cams the sheet 8 into closercontact with sheet 7. An increased pull on the mandrel 9 brings thereinforcing flange 4 into engagement with the bulge 13 forcing it tocollapse as shown. Then the mandrel 9 continues to pull the sheets 7 and8 together.

The rivet illustrated in FIGURES 11 to 16 is a further development ofthe tubular rivet shown in FIGURE 7. In this embodiment of the inventionthe elongated shank 15 of the rivet 14 has both a bulbous configuration16 and a neck 18 intermediate its length, The bulge 16 joins thereinforcing flange 4 at the tail end of the shank 15 by a short parallelportion 17. At its opposite end the bulge 16 merges into the neckportion 18. A diverging conical shank portion v19' joins the neck 18with a rivet head 20 which is counterbored at 21 to give relief to thebroaching mandrel 22 as will be later explained. The rivet 14 isthreaded over the mandrel 22 which has a cylindrical head 23 tapering attowards the junction with its stem 24. As illustrated in FIGURE 11 theconcal portion 25 of the mandrel 22 diverges from its stem 24 at a point24:: towards the head 23 so that its faces 25 form an included angle ofapproximately 60". This angle may vary, the magnitude of the angledepending upon the axial thickness of the reinforcing flange 4 of therivet 14.

In use the mandrel 22- with the rivet 14- threaded tail first thereon isloaded into the gun and the rivet mandrel assembly is inserted into thehole 6 of the work 7 and 8 to be riveted. During breaching operation themandrel head 23 sinks into the reinforcing flange 4 of the rivet (seeFIGURE 13) causing the reinforcing flange 4 to work harden and toincrease its resistance to further expansion radially. As continuouspull is applied on the mandrel 22 the bulged portion 16 yields first tothe pressure on the flange and causes the bulge 16 to collapse andexpand radially as can be seen in FIGURE 14. Subsequent pull on themandrel overcomes the resistance to expansion offered by the reinforcingflange 4, and the mandrel head 23 expands the flange 4 and the shank 15,which lies within the rivet hole 6 in the work 7 and S, radially (seeFIGURE 15) so that when the mandrel 22 is pulled through the rivet 14,the material of the rivet shank 15 fills the 'hole 6 completely. Theformation of the counter bore 21 in the rivet head 20 prevents theextrusion of the surplus rivet material which has been shifted axiallyby the moving mandrel head 23. The surplus material of the inner Wall ofthe rivet shank 15 is flattened out by the passing of the head 23 of themandrel 22 therethrough, thus providing a parallel bore capable ofreceiving a sealing pin if required. It has been found that anyundesirable extrusion of rive-t material has been eliminated by theformation of a counter bore in the rivet head and of the constrictedportion or neck on the shank thus resulting in perfect clenching of thework to be riveted.

The purpose of the reinforcing flange 4 is to prevent the mandrel 9 or22 from expanding the tail end of the rivet shank until the collapse ofthe weakened zone 5 or 13 or 16 has been effected.

It will be understood that the bulge of the rivet shank can be weakenedby reducing its wall thickness in order to induce an early expansion orcollapse.

Furthermore, the hardness of the reinforcing flange 4 of the rivet 14may be increased by work hardening, so that additional pressure would berequired on the mandrel 9 or 22 to expand the flange 4.

The proposed method of manufacturing the rivet illustrated in FIGURES 11to 16 is to form external dimensions, drill, ream and part off, thenanneal and hydraulically form the bulge.

In the modification \of the invention as illustrated in FIGURES 17 and18 a tubular rivet 26 has an elongated parallel'shank portion 27 ofuniform wall thickness which merges into a conical portion 28 joiningthe shank portion 27 with a reinforcing flange 29 at the tail end of therivet 26. The rivet 26 is formed with two coaxial parallel bores '36 and31, the bore 39 extending from the head of the rivet 26 being of alarger diameter than the bore 31. The bore 30 tapers at 32 in thedirection of the bore 31. It has been found by tests with rivets havingA" shank diameter that the'most suitable angle of inclination of theconical portion 28 relative to the axis of the rivet is approximately19.

Preferably the wall thickness of the conical portion 28 of the rivet 26is approximately greater than that of the parallel shank portion 27 andin no case is it less than the actual thickness of this parallelportion.

The design of this rivet is based on the same principle as thatdescribed with reference to hydraulically preformed rivet illustrated inFIGURES 11 to 16, namely the controlled collapsing of a weakened wallsection of the rivet. The complementary mandrel is similar to that shownin FIGURE 11. The reinforcing flange 29 consti-tutes the strong zone,and the conical portion of the shank 28 and that part of the parallelshank portion 27 protruding at the inaccessible side of the sheets 7 and8 to be riveted the Weak zone, or the collapsible part of the rivet uponthe initial pull of the mandrel 22.

The rivet 26 just described does not require to be hydraulicallypreformed. The manufacturing costs of this rivet are, therefore, moreeconomical than those illustrated in previous examples. The rivet 26 isproduced from cylindrical stock of metal by turning the shank portion 27and the reinforcing flange portion 29, cutting an annular groove 33 andthus forming the conical portion .23; drilling a hole to a diameterequivalent to that of bore 31, parting the rivet from the stock andcounterboring the rivet hole 31 to the size of diameter 30 and finishingthe rivet. For example when rivets 26 are made from AL 69 alloy it hasbeen found to be advantageous to treat the rivets in a solution ofneutral salts for 15 minutes at approximately 490 C. plus-minus andsubsequently plunge the rivets into cold Water. Age hardening iscompleted after approximately 5 to 10 days imparting necessary strengthto the rivets.

It will be understood that rivets above described may be made from othermaterials, for example B.51 SO aluminium alloy; Monel DTD 200A G & C;brass 70/ 30,

etc. Prior to broaching it is preferred to lubricate the rivet or themandrel. This may be effected in various ways.

Furthermore it may be preferable to use bar material in a semi hardcondition to facilitate machining, but such rivets will require anannealing operation in order to assist collapse of the rivet shankduring riveting.

The construction of the rivet and mandrel assembly described above maybe advantageously employed in magazine type riveting tools.

The bulbous portions 13 and 16, FIGURES 6 and 11 respectively, of therivet shank are preformed hydraulicwy, and the stem 24 of the mandrel 22is a sliding fit within the bore of the rivet at two localities. In theconstruction of the rivet shown in FIGURES 17 and 18 however, themandrel stem 24 is a sliding fit only within the bore 31 of thereinforcing flange 29 of the rivet 26. The remainder of the rivet shankis not supported by the mandrel stem 24 and in consequence the rivet 26may become out of alignment with the central line of the mandrel. Thiscauses an uneven collapse of the tail of the rivet during broaching. Toovercome this drawback a split ring 33 of soft material may be insertedin the counterbore 31 of the rivet head 32 (FIGURES 19 and 20) for thepurpose of centralising the mandrel 22 in the rivet during broaching.

In use a number of rivets 26 and split rings 33 threaded tail first onthe mandrel stem 24 are inserted in a magazine type riveting gun. Afterthe rivet is expanded the ring 33 in each rivet 26 is retained on themandrel upon the upsetting of the rivet until the return stroke of theriveting gun (not shown) when the ring 33 is ejected by a succeedingrivet 26. This requires very little effort due to the split in the ring33.

In the modification shown in FIGURE 21 the reinforcing flange 29 at thetail of the rivet 26 may be formed with a small cylindrical protrusion34 which projects into and is located in the counterbore 30 of theadjacent rivet 26.

It should be noted that with snap head rivets the possibility ofmisalignment during broaching is quite remote as the front jaws of thegun form sufficient bearing surface. With the countersunk head rivets,however, the gun jaws offer insuflicient bearing surface and it isnecessary to provide some form of axial control.

I claim:

1. In combination, a high clench headed tubular rivet and a broachingmandrel, said tubular rivet comprising a head, a shank, and a flange,said head, shank and flange portions having concentric longitudinalbores, said shank having a main substantially cylindrical portion and afrusto-conical portion connecting said main portion to said flange, thelatter portion having a periphery which progressively reduces inprogressing from said shank main portion to said flange, said flangeextending peripherally outwardly of said latter portion and having aradial thickness substantially greater than the Wall thickness of saidlatter shank portion, the bore in said flange being of lesser size thanthe bore in said shank and said head, said mandrel having a shankreceived in and extending longitudinally through said head, shank andflange, said mandrel having a shank formed complementarily to theperiphery of said bore in said flange, said mandrel having an enlargedhead of larger size than said bore in said flange and connected to themandrel shank by a section tapering from the periphery of the head tothat of the mandrel shank, the head being of a size to be freelyslidable lengthwise through at least the major portion of the length ofsaid shank, said mandrel shank being slidable in said flange bore, saidmandrel head and tapered portion being initially positioned to the otherside of said flange with respect to the shank portion of the rivet, andguide means frictionally mounted within said longitudinal bore extendingthrough said shank of said rivet comprising a centering means for saidmandrel and having a bore concentric with said bore in said flange andslidably receiving said mandrel shank, the bore in said centering meansbeing of a size smaller than the periphery of said head of said mandrel,the latter means being slidable outwardly of said rivet, when themandrel is drawn through the rivet.

2. The combination of claim ,1 wherein said centering means comprises asplit sleeve.

3. A tubular rivet for use in blind riveting operations Where a mandrelwith an enlarged head is drawn through the rivet from the tail endthereof to the head end thereof and expands portions of the rivet, saidrivet comprising a head, a shank, and a reinforcing flange, said headbeing connected to one end of said shank and said reinforcing flangebeing connected to the opposite end of said shank, said shank, saidhead, and said reinforcing flange having concentric longitudinal bores,said shank having a first portion and a second portion connected to saidfirst portion, said first portion being positioned adjacent said flangeand connected thereto, said second portion being intermediate said firstportion and said head, said second portion being of larger internaldiameter than that of said flange and larger than the diameter of thehead of said mandrel, said first portion being formed of a substantiallyuniform wall thickness and having a bore which decreases in diameterfrom the internal diameter of said second portion to the internaldiameter of said flange, said flange having a wall thicknesssubstantially greater than said first portion and extending radiallyoutwardly of the adjacent end of said first portion, the bore of saidflange being sufficiently large to receive the shank of said mandrel butsmaller than the head of said mandrel, an annular member frictionallymounted within the longitudinal bore of said shank at the head endthereof, said member having a bore concentric with the shank bore andbeing slidable outwardly of said bore of said shank, said bore of saidannular member being of substantially the same size as the bore in saidflange, whereby when a pulling force is applied between the shank of themandrel and the head of the rivet, the head of the mandrel first movessaid flange towards the head of the rivet and collapses the shank of therivet, producing outward bulging thereof, and continued movement of themandrel effects clenching of the bulged and collapsed shank portionsagainst the parts being riveted, and thereafter the mandrel head passesthrough said flange expanding the same, and removes said annular memberfrom the head of said rivet.

4. A rivet according to claim 3 wherein the periphery of said firstportion decreases progressively from said second portion of said shankto said flange.

5. A rivet according to claim 3 wherein said first portion is offrusto-conical shape with its apex positioned toward said flange and itsbase toward said second portion of said shank.

6. A rivet according to claim 3 wherein said member comprises a splitring.

7. In combination, a high clench headed tubular rivet and a breachingmandrel, said tubular rivet comprising a head, a shank, and a flange,said head, shank and flange portions having concentric longitudinalbores, said shank having a main substantially cylindrical port-ion and afrusto-conical portion connecting said main portion to said flange, thelatter portion having a periphery which 7 V progressively reduces inprogressing from said shank main portion to said flange, said flangeextending peripherally outwardly of said latter portion and having aradial thickness substantially greater than the wall thickness of saidlatter shank portion, the bore in said flange being of lesser size thanthe bore in said shank and said head, said mandrel having a shankreceived in and extending longitudially through said head, shank andflange, said mandrel having a shank formed complementarily to theperiphery of said bore in said flange, said mandrel having an enlargedhead of larger size than said bore in said flange and connected to themandrel shank by a section tapering from the periphery of the head tothat of the mandrel shank, the head being of a size to be freelyslidable lengthwise through at least the major port-ion of the length ofsaid shank, said mandrel shank being freely slidable in said flangebore, said mandrel head and tapered portion being initially positionedto the other side of said flange with respect to the shank portion ofthe rivet, and including an annular protruding portion projectingaxially from said flange on the side opposite from said rivet shank,said protruding portion having a central bore concentric with and ofsubstantially the same size as the bore in said flange, said protrudingportion having an outer periphery formed complementary to said bore insaid shank and being adapted to be received in the shank bore of asecond rivet to constitute a positioning member.

References Cited in the file of this patent UNITED STATES PATENTS Re.20,055 'Huok Aug. 4, 1936 927,064 Mower July 6, 1909 2,148,977 Buck Feb.28, 1939 2,255,650 Burke Sept. 9, 1941 2,384,321 Lees Sept. 4, 19452,612,073 Taylor Sept, 30, 1952 2,670,021 Torresen Feb. 23, 19542,887,926 Edwards May 26, 1959 FOREIGN PATENTS 737,284 France Oct. 3,1932 410,423 Great Britain May 17, 1934 982,415 France June 17, 1943596,275 Great Britain Dec. 31, 1947 613,882 Great Britain Dec. 3, 1948

